2018) and use of scent-detection dogs (Arnett 2006, Mathews et al. Fortunately, shorter search intervals (Smallwood et al. 2010) and low searcher detection of available carcasses (Smallwood 2017, Smallwood et al. Compared to measuring experimental treatment effects applied to animals the size of griffon vultures, measuring a treatment effect for small birds and bats is made even more difficult by low fatality detection rates owing to quick scavenger removal (Smallwood et al. Furthermore, finding zero fatalities might mean that none occurred or that fatalities occurred but none were found. However, finding zero fatalities following an action to reduce fatalities is difficult to interpret outside the context of a suitably designed experiment, such as a before-after, control-impact (BACI) experiment, and without knowing how many animals were normally killed by wind turbines prior to the action (Sinclair and DeGeorge 2016). ( 2017) reported no griffon vulture ( Gyps fulvus) fatalities following implementation of a detect-and-curtail strategy based on radar detections. Evidence is lacking for any attraction to operating turbines by flying birds, but Tomé et al. 2014), where they forage near and within the rotor plane (Horn et al. 2019), whereas a decade of seasonal curtailment did not appear to reduce bird fatalities in the Altamont Pass Wind Resource Area (APWRA) (Smallwood and Neher 2017).īats appear to be attracted to wind turbines (Cryan et al. Operational curtailment showed promise for reducing bat fatalities (Arnett et al. Careful micro-siting (i.e., the siting of wind turbines within a project based on specific flight behavior patterns) contributed to reduced fatality rates in repowered wind projects for select raptor species but might have inadvertently increased fatalities of other birds and bats (Brown et al. Whereas multiple mitigation measures have been proposed, promised, or required in conditional use permits in earlier wind projects, efficacy was poor or unquantified because of a lack of appropriate experimental design (Lovich and Ennen 2013, Sinclair and DeGeorge 2016), incomplete implementation, permit noncompliance, or fatality monitoring at search intervals that were too long for measuring mitigation treatment effects (Smallwood 2008). Because installed wind energy capacity in the United States doubled from 2012 to 2020, bird and bat fatalities likely also increased. In the United States, for example, wind energy generation in 2012 was estimated to have killed 600,000 (Hayes 2013) to 888,000 bats (Smallwood 2013), 214,000 to 368,000 small birds (Erickson et al. Wind energy development has expanded rapidly over the last 3 decades and wildlife ecologists have pursued mitigation strategies to minimize and reduce bird and bat fatalities caused by collisions with wind turbine blades. The Journal of Wildlife Management published by Wiley Periodicals, Inc. Because the migration season is relatively brief, seasonal curtailment would greatly reduce bat fatalities for a slight loss in annual energy generation, but it might not benefit many bird species. Of bird species represented by fatalities in study 2, 79% were found at inoperable wind turbines. In study 2, converting wind turbines from inoperable to operable status did not significantly increase bird fatalities, and bird species of hole or sheltered-ledge nesters or roosters on human-made structures died in substantial numbers at vacant towers. In study 1, wind turbine curtailment significantly reduced near-misses and rotor-disrupted flights of bats, and it significantly reduced fatalities of bats but not of birds. We also performed BACI experiments during a 3-year study of curtailment and operational effects on bird fatalities among wind turbines of varying operational status (study 2). We performed opportune before-after, control-impact (BACI) experiments of curtailment effects on bird and bat fatalities and nocturnal passage rates during fall migration at 2 wind projects, where 1 continued operating and the other shut down from peak migration to the study's end (study 1). Bird and bat fatalities increase with wind energy expansion and the only effective fatality-reduction measure has been operational curtailment, which has been documented for bats but not for birds.
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